Certain forms of cancer are believed to be less common when the diet contains dietary fiber. We are examining the physico-chemical properties of lignins in preparations partially or fully separated from plant fiber, thereby to provided a basis for hypotheses on the role of this constituent in the diet in relation to carcinogenesis. The binding of several carcinogens and co-carcinogens to these lignins is being studied. THe main emphasis is on nitrosamines and other nitrosocompounds and bile salts. Lignin may also influence carcinogenesis through its oxidation-reduction properties, and through reaction with nitrites. It can also bind metal ions and other significant substances in the diet. The study will thus illustrate the effect of lignin on the bioavailability of a variety of substances implicated in carcinogenesis.